1. Field of the Invention
The invention relates to a ballast architecture with wireless communication for activating a fluorescent lamp. More specifically, the invention relates to a ballast which includes a communication decoder, a lamp driver and a transceiver/receiver within the ballast enclosure.
2. Description of the Related Art
Lighting control in an office or commercial building has gone through several stages. The traditional control approach uses a separate control box outside the ballast, as shown in FIG. 1. The central control management for the whole building can also control the lighting through the network.
With the recent advancements in RF and semiconductor technology, wireless control is attracting more and more attention from people in the lighting industry. Currently there are some wireless control systems available in the market. A typical RF wireless control structure is shown in FIG. 2. As can be seen in the figure, the wires between the wall unit and the control box in FIG. 1 are replaced by a transmitter and receiver. This eliminates the vertical wiring and brings wireless advantages. However, the control box is still outside of the ballast.
An additional problem with prior art RF systems is isolation. For safety reasons, when the RF receiver/transceiver is wired to the ballast, there has to be some interface for high voltage isolation. This adds cost and complexity to the whole system. FIG. 3 shows the problem. The current state of the art uses a transformer or opto-isolation. FIG. 3 also shows the structure of the ballast. The digital decoder is used to decode the control command coming from the control box, it can be a microprocessor. The lamp driver consists of the power stage and the control IC. The power stage includes the high voltage driver, protection circuits, power storage and filter elements. The state-of-the-art for the control IC is the Alpha-based analog IC for controlling the power stage. Reference for Alpha IC is U.S. Pat. Nos. 5,680,017 and 5,559,395.
The current approach of lighting control faces the following challenges:
1. Cost: adding a separate box connected to the ballast increases the cost.
2. Power savings: if the power consumption information can be fed back from ballasts, the central management can easily improve the energy utilization. However, with the analog ballast, it is not easy to build a two-way communication link without extra cost.
3. Resolving the high voltage isolation problem described previously.
The invention is a new architecture for a high frequency (HF) ballast with wireless communication interface. The new architecture integrates the RF wireless interface into the ballast. A user control transmits an RF control signal to a second antenna at the ballast site which provides the RF signal to the ballast which activates the fluorescent lamp. The ballast includes a transceiver/receiver, a communication decoder, a power control stage and a power stage. The transceiver/receiver receives the RF signal and communicates it to the communication decoder which acts as an interface to the power stage control. The power stage control controls the power stage that activates the fluorescent lamp. The communication decoder, power stage control (analog or digital), power stage and transceiver/receiver are located within the ballast enclosure which is an important part of the invention. If the power stage control is digital it may be combined with the communication decoder into one microprocessor. The communication decoder may be a serial interface. The transceiver/receiver is an RF integrated circuit. The ballast further includes an isolator to isolate the transceiver/receiver from the second antenna. The isolator may be capacitive.